Orateur
Description
DNA in the nucleus is not randomly packed: it folds into 3D structures that help regulate genes and must be reestablished each time the cell divides. This folding is controlled by molecular motors that consume energy. For example, cohesin and condensin can actively pull DNA to form loops (“loop extrusion”). Because these processes use energy, they push chromosomes away from equilibrium conformations and create structures that can persist over time before relaxing. For example, during mitotic exit, the constraints established by condensins disappear and chromosomes undergo a major structural transition as interphase organization is rebuilt.
My project is to build a physical model of chromatin as a chain of connected segments and to introduce a way to quantify the internal “tension” along the polymer chain. This tension reflects two effects: random thermal motion that tends to expand the chain (osmotic), and constraints due to the bonds that resist deformation (elastic). By following how tension spreads along the chain and decays over time, the model explains how chromosomes gradually lose the “memory” of imposed loops or compaction.